B3 Organization and the digestive system Flashcards
Simple sugars
Small carbohydrates consisting of only one or two sugar molecules e.g. glucose and sucrose
Complex carbohydrates
Long chains of simple sugars e.g. starch and cellulose
Tissue
A group of cells with similar structure and function working together
Organ
A collection of tissues working together to perform a specific function
Organ system
A group of organs that all work together to perform specific functions
Food tests - carbohydrates
- Iodine test for starch, yellow-red iodine solution turns blue-black if starch is present
- Benedict’s test for sugars, blue Benedict’s solution turns brick red on heating if a sugar such as glucose is present
Food tests - protein
Biuret test - blue Biuret reagent turns purple if protein is present
Food tests - lipids
Ethanol test - ethanol added to a solution gives a cloudy white layer if a lipid is present.
Lock and key enzyme theory
- The substrate of the reaction to be catalysed fits into the active site of the enzyme
- The substrate is complementary in shape to the active site
- Once it is in place, the enzyme and the substrate bind together
- The reaction then takes place rapidly and the products are released from the surface of the enzyme
Metabolism
The sum of all the chemical reactions in a cell or the body
Effect of pH on enzyme action
- The shape of the active site of an enzyme comes from forces between the different parts of the protein molecule
- These forces hold the folded chains in place
- A change in pH affects these forces, and the shape of the molecule changes
- As a result, the specific shape of the active site is lost, the substrate is no longer complementary in shape to the active site, the enzyme no longer acts as a catalyst
Effect of temperature on enzyme action
- The rate of enzyme-controlled reactions increases as the temperature increases as molecules have more kinetic energy, only up until the optimum temperature
- The optimum temperature for enzyme action is approximately 37 degrees
- After this, the protein structure of the enzyme is affected by the high temperature and the active site changes shape
- The substrate will no longer fit in the active site, the enzyme is denatured and can no longer work as a catalyst
- The rate of the reaction drops dramatically
What are carbohydrates made up of?
Simple sugars
Function of small intestine
Digest food and absorb nutrients from digested food
Function of large intestine
Absorb water from digested food
Function of the gall bladder
Store bile before release into small intestine
Function of liver in the digestive system
Produces bile for lipid digestion
What are lipids made up of?
1 glycerol + 3 fatty acids
What are proteins made up of?
Amino acids
Name the reagent used to test starch
Iodine
What element make up proteins
Carbon, hydrogen, oxygen, nitrogen
Name the reagent used to test proteins
Biuret solution
Name the reagent used to test for sugars
Benedict’s solution
Name the reagent used to test for lipids
Ethanol(+water)
State risks of doing food tests
- Ethanol is flammable
- Biuret is corrosive
Function of salivary glands
Produce digestive enzymes e.g. amylase
Function of the stomach
Releases digestive enzymes to digest foods
Digesting carbohydrates
- Starch is one of the most common carbohydrates we eat. It is brown down into sugars in the mouth and small intestine. This reaction is catalysed by an enzyme called amylase
- Amylase is produced in the salivary glands, so the digestion of starch starts in the mouth
- Amylase is also made in the pancreas, no digestion takes place inside the pancreas
- All the enzymes made there flow into the small intestine, where most starch is digested
Digesting proteins
- The breakdown of protein food such as meat, fish, and cheese into amino acids is catalysed by protease enzymes
- Proteases are produced by the stomach, pancreas, and small intestine
- The breakdown of proteins into amino acids takes place in the stomach and small intestine
Digesting fats
- Lipids are broken down into fatty acids and glycerol in the small intestine
- The reaction is catalysed by lipase enzymes, which are made in the pancreas and the small intestine, the enzymes made in the pancreas pass into the small intestine
- Bile emulsifies the fats, breaks up large drops of fat into smaller droplets, provides a much bigger surface area of fats for the lipase enzymes to act upon
- The larger surface area helps the lipase chemically break down the fats more quickly into fatty acids and glycerol
What happens after digestion?
- Once the food molecules have been completely digested into soluble glucose, amino acids, fatty acids, and glycerol, they leave the small intestine
- They pass into the bloodstream to be carried around the body to the cells that need them
Which organs produce amylase?
Salivary glands and pancreas
Which organs produce proteases?
Stomach, pancreas, small intestine
Which organs produce lipases?
Pancreas and small intestine
Where does starch digestion occur?
Mouth and small intestine
Where does protein digestion occur?
Stomach and small intestine
Where does lipid digestion occur?
Small intestine
Why do enzymes not work well at lower temperatures?
Inactive, not enough kinetic energy to collide and bind to the active site
What is digestion?
Breakdown of large insoluble molecules into smaller soluble substances
What is emulsification?
Physically breaking down large oil drops into smaller droplets, increasing surface area for lipases to work on
What is the role of bile in the digestive system?
- Bile is an alkaline substance which neutralises the hydrochloric acid secreted by the stomach
- Bile emulsifies lipids to form droplets, this increases the surface area for the lipase enzyme to work on
what is the main function of the digestive system?
to digest food and absorb nutrients obtained from digestion
what is the role of the pancreas and salivary gland in the digestive system?
glands which produce digestive juices containing enzymes
what is the role of the stomach in the digestive system?
- produces hydrochloric acid
- which kills any bacteria present and provides the optimum acidic pH for the protease enzyme to function
what is the role of the small intestine in the digestive system?
where soluble food molecules are absorbed into the bloodstream
what is the role of the liver in the digestive system?
- produces bile
- which emulsifies lipids and allow the lipase enzyme to work more efficiently
what is the role of the large intestine in the digestive system?
absorbs water from undigested food, producing faeces
what is the role of enzymes in the digestive system?
act as biological catalysts which speed up the rate of biological reactions (the breakdown of food) without being used up
how does temperature affect enzyme action?
- up to a certain point, increasing temperature increases enzyme action
- as molecules have higher kinetic energy
- above optimum temperature, the shape of the active site is altered and the enzyme becomes denatured
- the substrate can no longer bind to the active site, so the reaction can no longer be catalysed
where are proteases produced in the body?
stomach, pancreas and small intestine
where are lipases produced in the body?
pancreas and small intestine
which organs in the human digestive system produce amylase?
salivary gland, pancreas and small intestine
